Mechanical pencil having means to prevent breakage of small diameter leads

ABSTRACT

The present disclosure is directed to a mechanical pencil having an internally threaded barrel, a slotted tube for containing a writing lead, means to cause relative rotation between the tube and the barrel, a lead propelling means, a clutch member for normally maintaining the writing lead in engagement with the propelling means, and means to prevent breakage of small diameter leads.

United States Patent Lockwood 1 Feb. 1, 1972 [54] MECHANICAL PENCIL HAVING MEANS TO PREVENT BREAKAGE OF SMALL DIAMETER LEADS [72] Inventor: John C. Lockwood, Atlanta, Ga.

Scripto Inc., Atlanta, Ga.

July 16, 1970 [21] AppLNu: 55,308

[73] Assignee:

[22] Filed:

[52] U.S.Cl ..401/58, 401/75 I51] 1nt.C1.. v...B43k 21/02, 843k 21/08 [58] Field of Search ..40l/68-77, 63,

[56] References Cited UNITED STATES PATENTS 2,866,438 12/1958 Schischkow ..401/74 X 3,205,862 9/1965 Brewer ...40l/76 X 3,537,799 1 H1970 Sakamoto ..401/76 X Primary ExaminerLawrence Charles Att0rney--Newton, Hopkins 8L Ormsby [57 ABSTRACT The present disclosure is directed to a mechanical pencil having an internally threaded barrel, a slotted tube for containing a writing lead, means to cause relative rotation between the tube and the barrel, a lead propelling means, a clutch member for normally maintaining the writing lead in engagement with the propelling means, and means to prevent breakage of small diameter leads.

4 Claims, 4 Drawing Figures MECHANICAL PENCIL HAVING MEANS TO PREVENT BREAKAGE OF SMALL DIAMETER LEADS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to improvements in mechanical pencils.

2. Description of Prior Art The present invention overcomes problems encountered in the prior art by affording a pencil construction which may be assembled and integrated within the barrel, from one end only, which in the present embodiment is shown as a rear end assembly. The invention includes a lead support means that is formed ofa hard, wear-resistant material and is ofa size such that the major diameter thereof is less than the cooperating diameters within the barrel. By virtue of the lead support means being formed of a wear-resistant material, it presents a writing tip that protrudes exteriorly of the barrel opening which is resistant to damage and deformation such as may be encountered when the writing instrument is dropped on a hard surface.

SUMMARY OF THE INVENTION The present invention is directed to a mechanical pencil construction which includes a means for supporting a small diameter lead in the form ofa stepped, tubular shell formed of a hard, wear-resistant material, one end of which is fixed to the main lead feed mechanism and the other end of which protrudes exteriorly of the barrel tip opening.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a side elevation, in partial section, showing the mechanical pencil of the present invention;

FIG. 2 is an enlarged partial longitudinal section of the forward tip portion shown in FIG. 1 with the lead propelling means protruding exteriorly of the lead support means;

FIG. 3 is an enlarged partial longitudinal section similar to FIG. 2 showing the lead propelling means contacting a lead that is supported both within the slotted tube and lead support means; and,

FIG. 4 is an enlarged elevation of the lead supporting means ofthe present invention.

DESCRIPTION OF THE ILLUSTRATED EMBODIMENT Referring now in detail to the embodiment chosen for the purposes of illustration, and in particular to FIG. 1, the mechanical pencil is generally designated by the numeral 10. The pencil includes an internally screw-threaded barrel 12 in which is disposed a tube 14 having a slot 16 that is longitudinally aligned with the axis of tube 14. Fixed to the front of the barrel 12 is a conical shell 17. At the rear end 18 of the barrel 12 is positioned a means 20 to cause relative rotation between the tube 14 and the barrel 12. The means 20 for causing rotation includes a drive cap 22 that is fixedly mounted on the tube 14. About the drive cap 22 is positioned ferrule 24 which at its rear end carries eraser 26. Within the forward portion of ferrule 24 is positioned lock sleeve 28 which is fixedly attached to the rear end 18 of the barrel 12. The frictional contact that is achieved between the lock sleeve 28 and the drive cap 22 affords sufficient resistance to the lead being moved rearwardly when brought in contact with the writing surface and in essence provides what is known in the writing instrument industry as backup" friction. Further, the frictional engagement between the ferrule 24 and the driving cap 22 provides the necessary means for causing rotation between the tube 14 and the barrel 12. It will be seen that within the forward portion of the ferrule 24 is disposed a clip member 30 that has ear portions that circumferentially surround the barre] 12 being disposed within the forward portion of the lock sleeve 28 and an annular groove 29 of barrel 12.

Referring to FIG. 2, it will be seen that a lead propelling means 32 is positioned so as to have a forward portion 34 disposed within the tube 14 and a nut portion 36 positioned exteriorly of the tube 14 having a threaded portion 38 that cooperates with the threads 40 of the barrel 12. The nut portion 36 is joined to the forward portion 34 by a web section 35 disposed within slot 16 of tube 14. A clutch member 44 is positioned within the interior wall of tube 14 and about the forward portion 34 of the lead propelling means 32 for normally maintaining engagement of the propelling means with the writing lead L, as shown in FIG. 3. When the writing lead nears exhaustion, the clutch 44 is allowed to move laterally because the dimple portion 46 can now move within the space 48 as shown in FIG. 2, thereby allowing the lead propelling means 32 to eject the remaining lead portion.

Referring in particular to FIG. 2 and 3, it will be seen that lead support means 50 of the present invention is fixedly at tached to the tube 14 by a dimple or stake 52. By this arrangement, relative rotation and axial longitudinal movement between the tube 14 and support means 50 is obviated. It should be noted that support means 50 is a stepped tubular shell and that the forward tip 54 is of a reduced diameter and has an internal diameter which is approximately the same as the diameter of the writing lead which lends lateral support to the writing thereof. It should further be noted that the lead support means is formed of a hard, wear-resistant metal such as drawn stainless steel which is resistant to damage such as deformation and the like which may be encountered if the item inadvertently strikes a hard surface. It shouid also be noted that while the lead support means possesses great strength and rigidity, it is formed of thin wall material, in the neighborhood of ten-thousandths of an inch, thereby presenting a small diameter writing tip exteriorly of the barrel. Breakage is also minimized by the fact that the extension of the writing lead forwardly of the lead support means 50 may be held to a minimum since a readily visible and distinct lead writing portion is presented exteriorly of the support means.

Iclaim:

1. In a mechanical pencil of the type including an internally screw-threaded barrel, a tube formed with a slot therein aligned with the axis of the tube, means to cause relative rota tion between said tube and said barrel, a writing lead propelling means mounted to travel in said tube and having a nut portion positioned exteriorly of said tube and in engagement with the internal screw threads of said barrel, a clutch member positioned within said tube and about the forward portion of said lead propelling means, the improvement comprising a stepped tubular member having a first diameter portion and a second portion of a reduced diameter, said first diameter portion being fixedly positioned at the forward portion of said slotted tube and being of a lesser diameter than the internal screw threads of the barrel and said second portion of said stepped tubular member being positioned in the forward tip of said barrel and having its most forward end projecting from said barrel, the internal diameter of said second portion being substantially identical to the diameter of the lead which is fed therethrough so that a lead of small diameter may be closely supported at the point thereof thereby minimizing lead breakage, the wall thickness of said stepped tubular member being substantially uniform throughout so that the interior diameter of said first diameter portion is larger than that of said portion of reduced diameter, the interior diameter of said first diameter portion being large enough to permit the entry of said clutch portion whereby said clutch portion is enabled to move to a point closely adjacent the forward tip of said barrel.

2. In a mechanical pencil, the combination as claimed in claim 1 and further characterized in "that the said tubular member is of a hard drawn metal that is resistant to wear and deformation.

3. In a mechanical pencil, the combination as claimed in claim 1 and further characterized in that said tubular member is attached to the said slotted tube by means of a stake portion of said tubular member being disposed in an aperture formed in said slotted tube.

4. In a mechanical pencil, the combination as claimed in claim 1 wherein a substantially conical shell surrounds the forward end of the said barrel and is fixedly attached thereto. 

1. In a mechanical pencil of the type including an internally screw-threaded barrel, a tube formed with a slot therein aligned with the axis of the tube, means to cause relative rotation between said tube and said barrel, a writing lead propelling means mounted to travel in said tube and having a nut portion positioned exteriorly of said tube and in engagement with the internal screw threads of said barrel, a clutch member positioned within said tube and about the forward portion of said lead propelling means, the improvement comprising a stepped tubular member having a first diameter portion and a second portion of a reduced diameter, said first diameter portion being fixedly positioned at the forward portion of said slotted tube and being of a lesser diameter than the internal screw threads of the barrel and said second portion of said stepped tubular member being positioned in the forward tip of said barrel and having its most forward end projecting from said barrel, the internal diameter of said second portion being substantially identical to the diameter of the lead which is fed therethrough so that a lead of small diameter may be closely supported at the point thereof thereby minimizing lead breakage, the wall thickness of said stepped tubular member being substantially uniform throughouT so that the interior diameter of said first diameter portion is larger than that of said portion of reduced diameter, the interior diameter of said first diameter portion being large enough to permit the entry of said clutch portion whereby said clutch portion is enabled to move to a point closely adjacent the forward tip of said barrel.
 2. In a mechanical pencil, the combination as claimed in claim 1 and further characterized in that the said tubular member is of a hard drawn metal that is resistant to wear and deformation.
 3. In a mechanical pencil, the combination as claimed in claim 1 and further characterized in that said tubular member is attached to the said slotted tube by means of a stake portion of said tubular member being disposed in an aperture formed in said slotted tube.
 4. In a mechanical pencil, the combination as claimed in claim 1 wherein a substantially conical shell surrounds the forward end of the said barrel and is fixedly attached thereto. 